Method and apparatus for removing ions from soil

Abstract

A method and apparatus for selectively removing species of ions from an area of soil. Permeable membranes 14 and 18 impregnated with an ion exchange resin that is specific to one or more species of chemical ions are inserted into ground 12 in close proximity to, and on opposing sides of, a soil area of interest 22. An electric potential is applied across electrodes 26 and 28 to cause the migration of ions out of soil area 22 toward the membranes 14 and 18. Preferably, the resin exchanges ions of sodium or hydrogen for ions of mercury that it captures from soil area 22. Once membranes 14 and 18 become substantially saturated with mercury ions, the potential applied across electrodes 26 and 28 is discontinued and membranes 14 and 18 are preferably removed from soil 12 for storage or recovery of the ions. The membranes are also preferably impregnated with a buffer to inhibit the effect of the hydrolysis of water by current from the electrodes.

What is claimed is: 
     
       1. A method for removing at least one species of ions from an area of soil having groundwater, said method comprising the steps of: placing at least two electrodes in spaced relation with respect to each other and to said area of soil;   placing a permeable barrier adjacent each of said at least two electrodes and said area of soil, said barrier adapted to pass said groundwater, said barrier carrying an ion exchange resin, said resin being selective for said at least one species of ions; and   applying a potential across said electrodes, said potential causing said at least one species of ions to migrate with respect to said electrodes, thereby allowing said ion exchange resin carried in said permeable barrier to capture said species.   
     
     
       2. The method as recited in claim 1, wherein said permeable barrier further comprises buffers, said buffers enabling said at least one species of ions to be captured by said resin. 
     
     
       3. The method as recited in claim 1, wherein said method further comprises removing said permeable barrier from said area of soil when said resin carried by said barrier is approximately saturated. 
     
     
       4. The method as recited in claim 1, wherein said permeable barrier is a hydrophilic polymer membrane. 
     
     
       5. The method as recited in claim 1, wherein said ion exchange resin is mercury specific. 
     
     
       6. The method as recited in claim 1, wherein said ion exchange resin is distributed uniformly throughout said permeable barrier. 
     
     
       7. The method as recited in claim 1, wherein said at least two electrodes are made of titanium. 
     
     
       8. A method for removing a plurality of mercury ions from a contaminated area of soil having groundwater, said method comprising the steps of: placing an anode and a cathode a distance apart from said contaminated area of soil, said anode and cathode in spaced relation with respect to each other and to said contaminated area of soil;   placing a first and second hydrophilic polymer membrane adjacent each of said anode and cathode, said first and second membranes spaced apart so as to define an active region therebetween, said contaminated area of soil generally contained within said active region, said first and second membranes each impregnated uniformly with a mercury specific ion exchange resin; and   applying a potential across said anode and cathode, said potential causing said plurality of mercury ions to migrate with respect to said anode and cathode through said membranes, thereby allowing said resins to capture said mercury ions.   
     
     
       9. The method as recited in claim 8, wherein said first and second membranes are further impregnated with buffers, said buffers dispersed uniformly throughout a portion of said first and second membranes, said portion being adjacent said electrodes. 
     
     
       10. The method as recited in claim 8, wherein said method further comprises removing said first and second membranes from said area of soil when said membranes are substantially saturated. 
     
     
       11. The method as recited in claim 8, wherein said cathode and said anode are both made of titanium. 
     
     
       12. The method as recited in claim 8, wherein said first and second membranes are spaced approximately 10 feet apart and said electric potential is approximately 60 volts DC.